Question 369083:  (1). Determine the critical region and critical values for z that would be used to test the null hypothesis at the given level of significance, as described in each of the following:   
 
(A) Ho:u >/_81 and,Ha:u<81,   a = 0.05 
         (> with line under)
 
(B) Ho:u= 45 and Ha:u (=/)45,   a = 0.10 
                           
 
(C)Ho:u  and Ha:u > 88,   a = 0.01 
       (< with line under)
 
 
 
 Answer by ewatrrr(24785)      (Show Source): 
You can  put this solution on YOUR website!   
Hi, 
The critical regions appropriate to be used to test the null hypothesis will 
depend on the parameters set by Ho & Ha.  In general: 
	a	a/2	crtical regions	 
90%	10	5%	z <-1.645	z >+1.645 
95%	5	2.50%	z <-1.96	z >+1.96 
98%	2	1%	z <-2.33	z >+2.33 
99%	2	0.50%	z<-2.575	z >+2.575 
For example when testing the Ho, the following would be used and will result 
in a negative or positive number depending on the value of X used in the 
test statistic =  	
 
(A) Ho: u ≥ 81 and Ha: u <81, a = 0.05 
this will result in a negative test statistic as the test value used for X < u 
therefore, the critical region would be z < -1.96
 
(B) Ho: u= 45 and Ha: u<45 or>45, a = 0.10 
The result for a test statistic here may be neg or positive depending on test value of X used 
therefore, the critical regions would be z< -1.645 or z > +1.64
 
(C)Ho: u ≤ 88, a = 0.01 
The result for this test statistic will be positve because test value used for X > u 
therefore, the critical regions would be  z > +2.33 
Hope this helps to clear this up.
 
 
  
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